1. Technical Field
The present invention relates in general to dynamic electrical testing and, in particular, to an improved system, method, and apparatus for low cost, high throughput dynamic electrical testing by multiplexing test sites with shared electronics.
2. Description of the Related Art
Data access and storage systems generally comprise one or more storage devices that store data on magnetic or optical storage media. For example, a magnetic storage device is known as a direct access storage device or a hard disk drive (HDD) and includes one or more disks and a disk controller to manage local operations concerning the disks. The hard disks themselves are usually made of aluminum alloy or a mixture of glass and ceramic, and are covered with a magnetic coating. Typically, one to five disks are stacked vertically on a common spindle that is turned by a disk drive motor at several thousand revolutions per minute (rpm).
A typical HDD also uses an actuator assembly to move magnetic read/write heads to the desired location on the rotating disk so as to write information to or read data from that location. Within most HDDs, the magnetic read/write head is located within a slider, which is mounted on a suspension. The suspension generally serves to mechanically support the head and any electrical connections between the head and the rest of the disk drive system. The slider is aerodynamically shaped to glide over moving air in order to maintain a uniform distance from the surface of the rotating disk, thereby preventing the head from undesirably contacting the disk.
A slider is typically formed with an aerodynamic pattern on its air bearing surface that enables the slider to fly at a constant height close to the disk during operation of the disk drive. A slider is associated with each side of each disk and flies just over the disk's surface. Each slider is mounted on a suspension to form a head gimbal assembly (HGA). The HGA is then attached to a semi-rigid actuator arm that supports the entire head flying unit.
During the manufacturing of HGAs, dynamic electrical testing (DET) is performed on the drives to assure quality products. DET equipment generally comprises a spin stand, the electronics, and software. The spin stand comprises a spindle including a disk supporting mechanism, an HGA fixture, and a head loading mechanism. The electronics includes controllers and a read/write analyzer (RWA) to generate and analyze waveforms. DET equipment is fabricated by several different companies but typically involves a single RWA having a single spin stand that can only test one HGA for an HDD at a time. Since DET equipment is relatively expensive and the process is time consuming, DET testing adds significant cost to the end products. Although one type of DET tester offers two channels on one spin stand for testing two HGAs at a time, the cost is high and the throughput remains relatively low. Some manufacturers compensate for this bottleneck by limiting DET to only a sample of their total production.
However, HGA manufacturers prefer 100% DET to achieve high HDD yield and reliability. Unfortunately, the investment for tester equipment and facilities is a significant portion of the total cost of the products. Thus, an improved solution for cost effective DET with lower equipment cost at higher throughput would be desirable.